Origen de la Vida! Cumbre Mundial de Evolución

Jeffrey L. Bada & Ada Yonath presentaron en el segundo día de la Cumbre Mundial de Evolución 2009 dos charlas increibles sobre el Origen de la Vida! Participantes y periodistas quedaron fascinados con estas intervenciones!
"El Legado de Darwin y el Origen de la Vida" se tituló la charla presentada por el Dr. Jeffrey L. Bada del Scripps Institution of Oceanography, University of California at San Diego.

Charles Darwin escribió en 1871 “Pero si (y oh! que gran y) podríamos concebir un pequeño charco tibio donde diferentes sales de amónia y fosfóricas, luz, calor y electricidad estuviesen presentes, donde un compuesto proteínico fuese quimicamente formado...
Con esta famosa frase, Jeffrey Bada inició su charla describiendo como Darwin describió los dos requisitos fundamentales para la vida: agua líquida y polímeros orgánicos. El clásico experimento de Miller de 1953 legitimizó el "pequeño charco tibio" de Darwin demostrando que las moléculas básicas de la vida podían ser sintetizadas bajo condiciones de la Tierra primitiva. Los procesos que dieron origen a la vida son cada vez mejor conocidos, y ahora es posible afirmar que:
"Si agua y compuestos orgánicos estuvieron o estan presentes en otros cuerpos de Universo, es rasonable asumir que pasos similares a los que dieron origen a la vida en la Tierra pudieron ocurrir en otros planetas" J. Bada.
Por su parte, la Dra. Ada Yonath del Instituto Weizmann de Israel presentó una impresionante charla sobre uno de los mayores descubrimientos de la década, la identificación de una maquina proto-RNA dentro de la ribosoma moderna, un verdadero "fosil molecular"!
"Las Ribosomas son las maquinas celulares universales para la interpretación del código genético de todos los organismos... Usando métodos estructurales, en conjunto con experimentos mutagénicos y cálculos de mecánica cuántica, hemos identificado dentro de la actual ribosoma el elemento arquitectural interno que representa una antigua versión de esta maquinaria" dijo Ada con emoción.
El trabajo de Ada Yonath es revolucionario y le ha merecido importantes reconocimientos como el premio Wolf en Química y el premio de la UNESCO para Mujeres en la Ciencia, dos de los mayores galardones científicos.

A continuación presentamos los resúmenes de las charlas de Jeffrey Bada y Ada Yonath:

Darwin’s Legacy and the Origin of Life by Jeffrey Bada
In Chapter XV of Origin of Species, Charles Darwin noted “It is no valid objection that science as yet throws no light on far higher problem of the essence or origin of life. Who can explain the essence of the attraction of gravity?” But by 1871 in a letter to his friend Joseph Dalton, Darwin had clearly changed his mind about the intractable question of life’s origin: “But if (and oh what a big if) we could conceive in some warm little pond with all sort of ammonia and phosphoric salts, light, heat, electricity present, that a protein compound was chemically formed, ---”. It is now generally accepted that there are two fundamental requirements for life as we know it, liquid water and organic polymers, such as nucleic acids and proteins. Water provides the medium for chemical reactions and the polymers carry out the central biological functions of replication and catalysis. During the accretionary phase of the young Earth, high surface temperatures would have made the presence of liquid water and an extensive organic carbon reservoir unlikely. As the Earth's surface cooled, water and simple organic compounds could have begun to accumulate. The classic 1953 Miller experiment legitimized Darwin’s “warm little pond” by demonstrating that the basic molecules of life could be synthesized from the gases present in the atmosphere of the early Earth. This type of prebiotic synthesis could have provided the raw material for the process of chemical evolution to begin. One of the central facets of this process was the synthesis of biologically important polymers, some of which had simple catalytic functions. Increasingly complex macromolecules were produced, and eventually molecules with the ability to catalyze their own imperfect replication appeared. Thus began the processes of multiplication, heredity and variation, which marked the point of both the origin of life and evolution. Once simple self-replicating entities originated they evolved first into the RNA World and eventually to the DNA/Protein World, which had all the attributes of modern biochemistry. If water and organic compounds were, or are, present on other bodies in our solar system and beyond, it is reasonable to assume that a similar series of steps that gave rise of life on Earth could occur elsewhere.
The identification of a proto-RNA machine in the modern ribosome by Ada Yonath
Ribosomes, the universal cellular machines for the translation of the genetic code into proteins in all organisms, are large riboprotein assemblies in which the decoding and the peptide bond formation sites are composed solely of RNA. Using structural methods, supported by comprehensive mutagenesis experiments and quantum mechanical calculations, we have identified within the concurrent ribosome the internal architectural element that represents the ancient version of this machine, s it confines a void that provides the stereochemistry required for peptide bond formation, for substrate-mediated catalysis, and for the succession of this reaction, hence capable of amino acid polymerization.
The overall fold of the RNA backbone of this region, which is comprised of 180 nucleotides, resembles motifs identified in ancient as well as in modern RNA molecules and exhibits pseudo two fold symmetry in all known ribosome structures. Consistently, the extremely high conservation of this region and its central location within the modern ribosome implies its existence irrespective of environmental conditions, indicate that it may represent the proto-(or minimal-) ribosome and support the hypothesis that the proto-ribosome evolved by gene duplication or gene fusion that underwent further functional optimization, required for the accommodation of two similar, albeit not identical, substrates
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Fotografías:(1) Aminoácidos, los bloques constructores de la vida, pueden formarse en el espacio! por ESA 2002.
(2) Jeffrey Bada por El Comercio
(3) Ada Yonath por
Koby Kalmanovich

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